Sapphire is a crystal that is generated in such a way that alumina (Al2O3) is melted at a temperature of 2050° C. and grows while being cooled slowly. As a single crystal of alumina, sapphire has light transmission properties across a wide wavelength range, and also has superior mechanical properties, heat resistance and corrosion resistance, as well as high hardness, heat conductivity, electrical resistance and impact resistance. Since sapphire has no pores and has high dielectric strength, it may be used for a substrate for epitaxial growth.
Representative methods of growing sapphire single crystal include a Verneuil method, an HEM (Heat Exchange Method), an EFG (Edge-Defined Film-Fed Growth), a Czochralski method, and a Kyropulous method.
The Kyropulous method has advantages in that equipment is relatively inexpensive, the manufacturing cost is low, and fewer defects result than when using the Czochralski method. According to the Kyropulous method, although similar to the Czochralski method, a single crystal is grown merely by pulling up the single crystal, without rotation of the single crystal.